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  <title>Document</title>
  <script>
    function unique(arr) {
      var newArr = [];
      for (var i = 0; i < arr.length; i++) {
        if (newArr.indexOf(arr[i]) === -1) {
          newArr.push(arr[i])
        }
      }
      return newArr;
    }
    var demo = unique(['c', 'a', 'z', 'a', 'x', 'a', 'x', 'c'])
    console.log(demo);
  </script>
</head>

<body>

</body>

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